Lost my series after winning a game? seriously riot?

I went on a multi game win streak and got into my promos, losing the first game. Next game, I'm winning my lane and the overall game hard and we're 17 minutes in with 4-5 towers destroyed. Then, my internet goes out right after taking the inner mid turret, and when I reconnect 7 minutes later my team had already forced them to surrender. We won the game, putting me at 1-1 in promos. I log onto my account, to see that I had fallen all the way down to the previous division with 64lp. After winning a game. So riot, you're telling me even though I won my game, I lost series? Seriously? I'd played all week to get there, only to discover I have to win 5 more games in a row to get back to the position I was in? How is this deemed acceptable in any way shape or form. So I lose lp when people dc on my team, and I also lose lp for winning a game? Seriously not cool at all rito.
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